The scarring has two main sources. Risso's dolphins rake each other with their teeth during social interaction, leaving long paired scratches that heal white and do not fade. Their squid prey, taken at depth, can also mark the skin with beak and sucker damage. Because the scars persist, the pattern accumulates rather than turning over, and an animal's apparent whiteness tracks its age.
The teeth themselves are unusual. Adults have no upper teeth and typically only two to seven pairs in the lower jaw, sometimes worn away entirely in old individuals. That dentition suits an animal that grips soft-bodied squid rather than seizing fish.
The pattern is useful but imprecise. Scar accumulation makes Risso's dolphins easy to identify individually from photographs, and gives a coarse sense of relative age, but no calibration lets a photograph yield a number of years, and scarring rates likely vary with how social an individual is.